It is standard practice to provide delicate process monitoring equipment in a potentially harmful environment like an oil refinery or cracking plant in a special cabinet or locker that shields it from harmful airborne materials and sudden temperature variations. Without such protection much electronic equipment would have a very short service life.
Such a cabinet must therefore be a solid freestanding unit that can be closed tightly. Its walls must be of insulating material, and it must be provided internally with appropriate hardware for mounting the equipment to be protected. Standard rack mounting is normally employed. Thus the inner surfaces of the walls are provided with the necessary formations.
As a rule the inner and outer surfaces of the walls are formed with square teeth, making it easy to mount things on them and bond things to them. Such irregularities on both the inside and outside faces of the walls make them unattractive to start with, and cause them to trap dirt so that they rapidly become even more unattractive. At the same time, such cabinets cannot normally be allowed to get very dirty, as in the conditions they work under the foreign matter clinging to them can be highly corrosive.
When the faces of the walls of such a cabinet are of aluminum, corrosion becomes a problem in many environments encountered in industry, particular airborne salts. Nonetheless aluminum is used to impart the necessary strength to the assembly.